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Stimulating Asphaltenic Oil Reservoirs, Experimental Investigation of Asphaltenic Sludge Formation to Plan Its Prevention

Sisakhti, Hossein | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50111 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ayatollahi, Shahaboddin; Shad, Saeed
  7. Abstract:
  8. Formation damage is probable to occur while drilling, work-over operations, and well completion in near wellbore zone due to different reasons; which leads to excess pressure drop through this area. Well stimulation operations are proposed to remove these damages and improve oil production; among which, acidizing is known as a traditional applicable method to stimulate oil and gas wells. Although this approach is accepted and chosen as a well stimulation method to remove formation damages, its poor design and implementation results in new formation damages. One of these arises when acid contacts asphaltic oil, which causes asphaltene particle instability and asphaltic sludge rapid precipitation in the formation. This precipitation phenomenon classified in very harsh formation damages category and is recommended to be controlled and prevented. In this research, the damage caused by the contiguity of typical applied acids in carbonate formations (HCL) with Kupal-Bangestan oil reservoir is investigated; also the propensity of asphaltic sludge formation and precipitation under static (bottle test) and dynamic (core flood) conditions is evaluated. Furthermore, utilizing experiment designing, the influential parameters in static condition were studied. In order to prevent this phenomenon, the efficiency of emulsified acid in an aromatic solvent regarding asphaltic sludge formation will be investigated. The results indicate that hydrochloric acid strongly tends to form asphaltic sludge contacting the mentioned oil. Temperature increase, acid to oil mixture ratio being 1:1, and presence of a ferric ion intensifies the sludge precipitation. In addition, the asphaltic sludge formed by emulsified solvent acid in absence of ferric ion is highly negligible compared with that formed by hydrochloric acid. While ferric ion is involved ( up to 2000 ppm), the ratio of the formed sludge by emulsified solvent acid to that formed by HCl averagely equals 0.18. Applying dynamic experiments, the permeability of polymeric fibers (which does not react with acid), saturated by oil, decreases to 0.63 of initial value after HCl injection and asphaltic sludge is evident in the texture of the fibers. However, injecting emulsified solvent acid, permeability alteration is insignificant and not any asphaltic sludge in the texture of fibers is observed
  9. Keywords:
  10. Formation Damage ; Acidizing Treatment ; Privention ; Asphaltenic Oil ; Sludge ; Stimulation Injection

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